Doris SQL: Support Doris Dialect

Summary

Add Doris SQL dialect, covering the core Doris syntax needed to parse common Doris DDL and load statements.

Motivation

Apache Doris has SQL syntax that differs from the generic SQL dialect, especially around CREATE TABLE clauses, key models, partition/distribution definitions, table properties, and Doris-specific load statements. A dedicated DorisDialect would let users parse Doris SQL without weakening generic parser behavior.

Proposed Scope

• Add DorisDialect
• Support Doris CREATE TABLE clauses:
  • ENGINE = OLAP
  • DUPLICATE KEY, UNIQUE KEY, AGGREGATE KEY
  • table COMMENT
  • PARTITION BY RANGE/LIST
  • AUTO PARTITION
  • DISTRIBUTED BY HASH/RANDOM
  • BUCKETS / BUCKETS AUTO
  • PROPERTIES (...)
• Support Doris column options such as AUTO_INCREMENT
• Support Doris LOAD DATA INFILE
• Support Doris CREATE ROUTINE LOAD
• Preserve generic dialect behavior where Doris-only syntax should remain rejected

Parser / AST Changes

• Add Doris-specific AST structures for key model, partition, distribution, table properties, and load statements
• Extend CreateTable with optional Doris-specific fields
• Add Display support for canonical SQL rendering
• Add span support for newly introduced AST nodes where applicable

Tests

Add Doris parser tests covering:

• Positive Doris parsing cases
• Generic/ANSI rejection cases for Doris-only syntax
• AST structure assertions
• Round-trip canonical rendering
• Escaping behavior for table comments containing single quotes